Integrated circuits (ICs) are typically assembled into electronic packages by physically and electrically coupling them to a substrate made of organic or ceramic material. One or more IC packages can be physically and electrically coupled to a substrate such as a printed circuit board (PCB) or motherboard to form an “electronic assembly”. The “electronic assembly” can be part of an “electronic system”. An “electronic system” is broadly defined herein as any product comprising an “electronic assembly”. Examples of electronic systems include computers (e.g., desktop, laptop, hand-held, server, etc.), wireless communications devices (e.g., cellular phones, cordless phones, pagers, etc.), computer-related peripherals (e.g., printers, scanners, monitors, etc.), entertainment devices (e.g., televisions, radios, stereos, tape and compact disc players, video cassette recorders, MP3 (Motion Picture Experts Group, Audio Layer 3) players, etc.), and the like.
In the field of electronic systems there is an incessant competitive pressure among manufacturers to drive the performance of their equipment up while driving down production costs. This is particularly true regarding the packaging of ICs, where each new generation of packaging must provide increased performance while generally being smaller or more compact in size. As market forces drive equipment manufacturers to produce electronic systems with increased performance and decreased size, IC packaging accordingly also needs to support these requirements. In addition, manufacturers of high-end IC packages, such as processors, are experiencing increasing demand for IC packages mounted in solderless or socketable packaging, because such packaging facilitates easy removal of the IC packages for testing, repair, replacement, and/or upgrading.
An IC substrate may comprise a number of metal layers selectively patterned to provide metal interconnect lines (referred to herein as “traces”), and one or more electronic components mounted on one or more surfaces of the substrate. The electronic component or components are functionally connected to other elements of an electronic system through a hierarchy of electrically conductive paths that include the substrate traces. The substrate traces typically carry signals that are transmitted between the electronic components, such as ICs, of the system. Some ICs have a relatively large number of input/output (I/O) terminals (also called “lands”), as well as a large number of power and ground terminals or lands.
Surface mount technology (SMT) is a widely known technique for coupling ICs to a substrate. One of the conventional methods for surface-mounting an IC on a substrate is called “controlled collapse chip connect” (C4). In fabricating a C4 package, the electrically conductive terminals or lands of an IC component are soldered directly to corresponding lands on the surface of the substrate using reflowable solder bumps or balls. The C4 process is widely used because of its robustness and simplicity. However, it does not provide a solderless or socketable package.
In addition to using SMT to couple an individual IC die to a substrate, whether at the IC package level or at a higher level such as a chip-on-board (COB) multi-chip module, it is also well known to use SMT to couple an IC package to a substrate such as a printed circuit board (PCB) or motherboard. Solder bumps, for example, can be employed between lands on the IC package and corresponding lands on the PCB.
As the internal circuitry of ICs, such as processors, operates at higher and higher clock frequencies, and as ICs operate at higher and higher power levels, the amount of loop inductance produced within IC packages and electronic assemblies can increase to unacceptable levels.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a significant need in the art for apparatus and methods for packaging an IC or an IC package on a substrate that provide a socketable connection, that minimize the thickness of the packaging, and that minimize loop inductance within the packaging.